The primary goal of this Mucosal Biology Scientific Research Support Component (SRSC) is to identify antibody effector functions at mucosal surfaces required to prevent HIV-1 acquisition, define how they differ by route of transmission, and through integrated studies across SRSCs (Mucosal, Vector, Non-human Primate) determine modes of protective antibody induction in non-human primates and in collaborative human clinical vaccine studies. Specific Aims Aim 1. To support CHAVI-ID by defining the functional nature of protective antibody responses at mucosal surfaces elicited in RV144 follow-on trials (RV306, RV328), in other HlV-1 vaccine trials (HVTN 204, 082, 076) and in the HVTN/CHAVI501 mosaic trial. Aim 2. To support CHAVI-ID by assessing the functional characteristics of protective antibodies at mucosal surfaces in NHP Core studies designed to determine optimal route/adjuvant combinations for the induction of mucosal immunity. Aim 3. To support CHAVI-ID by evaluating the functional characteristics of protective antibodies at mucosal surfaces in NHP and Vector SRSC studies designed to determine optimal vector strategies for the induction of mucosal immunity. Aim 4. To support CHAVI-ID by determining the impact of dimeric vs monomeric antibodies on mucosal acquisition.